Identification

Description

Valves are asymmetric, with a slightly narrow lanceolate to elliptic valve margin. Both apices, headpole and footpole, are distinctly capitate. In the studied population, the footpole is consistently more protracted than the headpole, creating the appearance of being somewhat “bent.” The axial area is linear and narrow. The raphe is straight and filiform. The proximal and distal raphe ends are simple. In the central area, striae are parallel to slightly radiate. The central area is asymmetric. In the central valve, a longer stria is near a punctate stigmoid. On the opposite side of the stigmoid, a short stria is present. Areolae not visible with LM.

Gomphonema lagenula is similar to G. parvulum, and many floras treat G. lagenula as a variety of G. parvulum. Gene sequences of these taxa, however, show that they are distinct from one another. The morphologic feature of capitate to rostrate apices has been considered a distinguishing feature of G. lagenula (Abarca et al. 2014), feature also noted by Patrick and Reimer (1966).

Thus, this taxon could be considered as a distinct species, or as a member of the G. parvulum species complex. The question is up to each practitioner, to determine how they wish to treat this taxon for their particular study goals. Gomphonema lagenula is included as both a species page and as part of the G. parvulum species complex on this website.

Autecology

This taxon is widespread across North America. Images included on this page are from a river in Georgia.

Links

Cite This Page

Johnson, K. (2018).
Gomphonema lagenula.
In Diatoms of North America.
Retrieved June 07, 2020, from https://diatoms.org/species/gomphonema-lagenula

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Gomphonema lagenula from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)STRAHLER = distribution plot of the Strahler Stream Order SLOPE = stream reach gradient (degrees)W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.PHSTVL = pH measured in a sealed syringe sample (pH units)log_COND = log concentration of specific conductivity (µS/cm)log_PTL = log concentration of total phosphorus (µg/L)log_NO3 = log concentration of nitrate (µeq/L)log_DOC = log concentration of dissolved organic carbon (mg/L)log_SIO2 = log concentration of silicon (mg/L)log_NA = log concentration of sodium (µeq/L)log_HCO3 = log concentration of the bicarbonate ion (µeq/L)EMBED = percent of the stream substrate that is embedded by sand and fine sedimentlog_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.

Gomphonema lagenula

Kütz. 1844

Apices capitate

Central area asymmetric

Footpole may be bent

Valves with capitate apices. The central area is asymmetric, with a shorter stria opposite the stigma. The footpole is often irregularly bent to one side.